The present invention relates to a device for controlling the rectilinear translation of a movable member, in particular a slide of a measuring machine, by means of which the movements of the movable member can be achieved with extremely low friction and very high precision.
It is known that to control the rectilinear translation of a movable member a pair of elements comprising a screw and a nut are usually utilised, to a first of which the movable member is fixed whilst the second is made to rotate by suitable drive means; normally, the movable member is axially connected to the screw, whilst the nut can turn with respect to the base of the machine but is axially restrained with respect to the base itself.
Although, with control devices of this type, even very high actuating forces can be transmitted to the movable member, and the displacements of this can be achieved with a good precision, there are nevertheless various disadvantages. In fact, rather high actuating forces on the nut are required, supplementary devices are necessary for ensuring a correct lubrication of the contacting surfaces of the screw and the nut, and normally deformations are induced which limit the application of this device in certain fields, for example in that of measurement machines. These disadvantages are a consequence of the high sliding friction which is generated between the contacting surfaces of the screw and the nut, in particular when large forces are required for the displacement of the movable member; to reduce the friction it is necessary to provide a very efficient lubrication, but even so, control of the displacement of the movable member requires rather high actuating couples which produce unacceptable deformations and which require very large dimensions of the various parts of the device which therefore makes them bulky.